Dewaxing hydrocarbon oil



Patented Sept. 15, 1936 5 swam HYDROCARBON on.

Ernest Frank Pevere, Beacon, N. YQassignor to The Texas Company, New York, N.

poration of Delaware Y.,. a cor- No Drawing. Application May 7, .1935, Serial No. 20,190

5 Claims. (Cl. 19619) This invention relates todewaxing hydrocarbon oil and more particularly to' ther emoval of wax from mineral lubricating oil stock for the production of low pour test lubricating oils.

The invention contemplates a solvent dewaxing process wherein a solvent selected from the dialkyl ethers of methylene, such as methylene dimethyl etheror methylal is employed. Methylal, for example, has the chemical formula CH2(OCH3)2 and may be prepared by reacting formaldehyde with methyl alcohol.

Instead of the dimethyl ether, methylal, it is contemplated that the diethyl and dipropyl ethers of methylene may also be employed, including both the iso and the normal forms of the dipropyl ether.

More specifically, the invention comprises mixing a wax-bearing mineral oil fraction with a solvent comprising methylal in proportions such that at temperatures of F. and below the solvent has substantially complete solvent action on the liquid constituents of the oil and substantially no solvent action upon the solid waxy constituents of the oil. This mixture is chilled to temperatures of the order of 0 F. and below, depending upon the desired pour test of the dewaxed oil, to precipitate the wax constituents. The precipitated wax constituents are then separated from the cold mixture by mechanical means such as filtration, centrifuging or settling.

I have discovered that methylal possesses properties which render it suitable as a dewaxing solvent. This solvent has anti-solvent properties for paraflin wax and in addition possesses comparatively high solvent power for mineral oil so that it may be employed alone as a satisfactory dewaxing solvent liquid. Its selective solvent action as between solid and liquid hydrocarbon constituents of wax-bearing mineral oil, at temperatures of around 0 F., is such that when dewaxing with this solvent liquid the pour temperature of the dewaxed oil will correspond to the dewaxing temperature and in some cases will have a pour temperature below the dewaxing temperature.

In some cases, as for example in the case of heavy viscous oils, such as residual cylinder stocks, it may be desirable to employ a diluent solvent in conjunction with the methylal. Accordingly in dewaxing such stocks, the wax-bearing oil may be mixed with a solvent mixture composed of methylal and solvent liquids of the character of benzol and its homologs or a light petroleum fraction, such as naphtha, or a petroleum fraction comprising mainly the normally gaseous hydrocarbons, such as propane and butane.

Inorder to more fully describe the invention, reference will now be made ,to the following example in which a wax-bearing distillate derived from Mid-Continent crude was dewaxed with methylal. The tests on the wax-bearing distillate were substantially as follows:

Gravity A.P.I 22.9 Saybolt Universal vis. at 210 F. '73 seconds Pour test 105 F.

One volume of the foregoing oil was mixed with three volumes of methylal. The resulting mixture was chilled to 6 F. to precipitate the wax constituents and while maintained at this temperature the cold mixture was filtered to separate the precipitated wax constituents.

The solvent was removed from the resulting filtrate by distillation and the remaining dewaxed oil amounting to about 70% of the original wax-bearing distillate, had a pour test of F. with a solid point at 8 F.

It will be observed that in the foregoing example the dewaxed oil had a pour test temperature of 11 below the dewaxing temperature.

The proportion of methylal to oil undergoing dewaxing may vary considerably from that specified in the foregoing example. Thus it is contemplated that the proportion of methylal to oil may be either less or greater than that mentioned, as for example, from 2 to 4 volumes of methylal to one volume of wax-bearing oil.

In the case of heavy viscous oils where it is desired to use a modifying or diluent solvent as already indicated, the proportion of methylal to diluent solvent will depend to some extent upon the character of the oil undergoing treatment and also upon the nature of the diluent being used. In the case of reduced residual cylinder stocks, for example, the proportion of methylal to diluent liquid may comprise around one part of methylal to 2 or 3 parts of diluent solvent.

The solvent of my invention is adapted to the separation of wax from petroleum oil or from either residual or distillate fractions thereof. It is also adapted to the treatment of Wax concentrates for the purpose of effecting the separation between the wax and oil constituents.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made Without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oil with a solvent comprising methylal, chilling the mixture to precipitate the wax constituents, and separating the precipitated wax constituents from the cold mixture.

2. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oil with methylal, chilling the mixture to precipitate the wax constituents, and separating the precipitated wax constituents from the cold mixture.

3. In the dewaxing of wax-bearing mineral. oil, the method which comprises mixing the oilwith methylal in the proportion of about one volume of oil and from two to four parts of methyl'al, chilling the mixture to a temperature of the order of 0 Rand below to precipitate the wax constituents, and removing the precipitated waxconstituents from the cold mixture.

4. In the dewaxing of heavy viscous wax-bearing mineral oil the method which comprises mixing the oil with a solvent composed of methylal and a diluent solvent of the character of benzol OR an.

where R-R represent alkyl radicals selected from the group consisting of methyl, ethyl and propyl, chilling the mixture to precipitate the wax constituents, and separating the precipitated Wax constituents from the cold mixture.

ERNEST FRANK PEVERE. 

